/* A C-program for MT19937: Real number version    */
/* genrand() generates one pseudorandom real number (double) */
/* which is uniformly distributed on [0,1]-interval, for each */
/* call. sgenrand(seed) set initial values to the working area */
/* of 624 words. Before genrand(), sgenrand(seed) must be  */
/* called once. (seed is any 32-bit integer except for 0).  */
/* Integer generator is obtained by modifying two lines.  */
/* Coded by Takuji Nishimura, considering the suggestions by */
/* Topher Cooper and Marc Rieffel in July-Aug. 1997.   */

/* This library is free software; you can redistribute it and/or */
/* modify it under the terms of the GNU Library General Public  */
/* License as published by the Free Software Foundation; either */
/* version 2 of the License, or (at your option) any later   */
/* version.              */
/* This library is distributed in the hope that it will be useful, */
/* but WITHOUT ANY WARRANTY; without even the implied warranty of */
/* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.   */
/* See the GNU Library General Public License for more details. */
/* You should have received a copy of the GNU Library General  */
/* Public License along with this library; if not, write to the */
/* Free Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA */ 
/* 02111-1307 USA             */

/* Copyright (C) 1997 Makoto Matsumoto and Takuji Nishimura.  */
/* Any feedback is very welcome. For any question, comments,  */
/* see http://www.math.keio.ac.jp/matumoto/emt.html or email  */
/* matumoto@math.keio.ac.jp          */

#include <stdio.h> 

/* Period parameters */ 
#define N 624
#define M 397
#define MATRIX_A 0x9908b0df /* constant vector a */
#define UPPER_MASK 0x80000000 /* most significant w-r bits */
#define LOWER_MASK 0x7fffffff /* least significant r bits */

/* Tempering parameters */ 
#define TEMPERING_MASK_B 0x9d2c5680
#define TEMPERING_MASK_C 0xefc60000
#define TEMPERING_SHIFT_U(y) (y >> 11)
#define TEMPERING_SHIFT_S(y) (y << 7)
#define TEMPERING_SHIFT_T(y) (y << 15)
#define TEMPERING_SHIFT_L(y) (y >> 18)

static unsigned long mt[N]; /* the array for the state vector */
static int mti=N+1; /* mti==N+1 means mt[N] is not initialized */

/* initializing the array with a NONZERO seed */
void
sgenrand(unsigned long seed)

{
	/* setting initial seeds to mt[N] using   */
	/* the generator Line 25 of Table 1 in   */
	/* [KNUTH 1981, The Art of Computer Programming */
	/* Vol. 2 (2nd Ed.), pp102]     */
	mt[0]= seed & 0xffffffff;
	for (mti=1; mti < N; mti++)
		mt[mti] = (69069 * mt[mti-1]) & 0xffffffff;
}

double /* generating reals */
/* unsigned long */ /* for integer generation */
genrand()
{
	unsigned long y;
	static unsigned long mag01[2]={0x0, MATRIX_A};
	/* mag01[x] = x * MATRIX_A for x=0,1 */

	if (mti >= N) { /* generate N words at one time */
		int kk;

		if (mti == N+1) /* if sgenrand() has not been called, */
			sgenrand(4357); /* a default initial seed is used */

		for (kk=0;kk < N-M;kk++) {
			y = (mt[kk]&UPPER_MASK)|(mt[kk+1]&LOWER_MASK);
			mt[kk] = mt[kk+M] ^ (y >> 1) ^ mag01[y & 0x1];
		}
		for (;kk < N-1;kk++) {
			y = (mt[kk]&UPPER_MASK)|(mt[kk+1]&LOWER_MASK);
			mt[kk] = mt[kk+(M-N)] ^ (y >> 1) ^ mag01[y & 0x1];
		}
		y = (mt[N-1]&UPPER_MASK)|(mt[0]&LOWER_MASK);
		mt[N-1] = mt[M-1] ^ (y >> 1) ^ mag01[y & 0x1];

		mti = 0;
	}

	y = mt[mti++];
	y ^= TEMPERING_SHIFT_U(y);
	y ^= TEMPERING_SHIFT_S(y) & TEMPERING_MASK_B;
	y ^= TEMPERING_SHIFT_T(y) & TEMPERING_MASK_C;
	y ^= TEMPERING_SHIFT_L(y);

	return ( (double)y / (unsigned long)0xffffffff ); /* reals */
	/* return y; */ /* for integer generation */
}

